Recently, miniaturization of a wiring in semiconductor devices has been advanced and the unevenness of a base substrate has become increasingly complex due to an increased aspect ratio and the like. Therefore, when an insulating film composed of a silicon oxide film or the like is formed on a substrate, for example on an semiconductor element, a forming method having good step coverage, being excellent in planarity and not adversely affecting the characteristics of the substrate is desired.
Conventionally, a method for forming a film by a thermochemical evaporation method using starting gases including a monosilane gas and oxygen as a producing method of a silicon oxide film is known. However the step coverage is not good so that a method by use of an organic-based silane gas such as tetraethoxysilane and ozone as starting materials has been examined.
Though the step coverage is good and the planarity is excellent in the case tetraethoxysilane is used as a starting material, it is necessary to set the deposition temperature usually to 400° C. or higher.
The silicon oxide film is manufactured by thermochemical vapor-phase deposition method, photochemical vapor-phase deposition method, plasma chemical vapor-phase deposition method and the like. However, there are problems in efficiency of manufacturing, that is, since high temperature is required to decompose or react a starting material by a heat in the thermochemical vapor-phase deposition method, however, and base materials on which a film is deposited are limited, and in the photochemical vapor-phase deposition method, while a film can be formed at low temperature, the window through which light is introduced is clouded and the deposition rate is low, being unfavorable.
In the plasma chemical vapor-phase deposition method, various methods for the silicone oxide film using a monosilane and an oxidizing agent such as oxygen and dinitrogen oxide as starting gases are examined. However, monosilane is hazardous and expensive, the use thereof is not industrially profitable, and the deposition temperature is high, therefore it is difficult to apply extensively in the methods.
A silane compound such as monosilane compound and disilane compound is used in various applications. In the field of a semiconductor, the silane compound is often used as a starting material to manufacture a silicon-based insulating film composed of silicon nitride, silicon oxide, silicon oxynitride by CVD method. That is, in the case a silane compound is used, a reaction with a nitrogen-containing reactable gas such as ammonia leads to a silicon nitride, a reaction with an oxygen-containing gas such as oxygen to a silicon oxide, and a reaction with a nitrogen-containing gas and an oxygen-containing gas to a silicon oxynitride.
There is a reaction where SiH4 gaseous starting material as a silane compound is oxidized with O2 for the standard production method of a silicon oxide by CVD method. Regarding the minimum design dimension of the semiconductor device, a thickness of the silicon oxide film has reached the stage as being counted by the number of layers of atoms accompanying high integration of an LSI in recent years. And it is required to lower the temperature of the process in order to reduce the problems of a heat-loading considering the miniaturization of an element structure.
Conventional CVD process using SiH4 gaseous starting material cannot flatten an uneven surface and a corrugated surface on the substrate. In addition, this CVD process, a void is formed in a space between narrow electrodes or in a trench of a gate to deteriorate significantly the film characteristics. Moreover SiH4 is an extremely dangerous starting material due to its self-ignitability.
In order to overcome the above failures, a reaction where tetraethoxysilane (hereinafter referred to as TEOS) as a liquid starting material instead of SiH4 is used and an oxidation with O3 is performed, is applied and has been made practical.
However, a film to be deposited by CVD method using TEOS still has problems in film quality such as minuteness, crack resistance and insulation properties. The substrate is required to be heated at 600 to 700° C. for forming a film while solving this problem. Accordingly, when a SiO2 film was formed on an aluminum wiring by CVD method using TEOS, there was a failure of deteriorating the aluminum wiring.
Moreover, a method for forming a silicon oxide film by reacting alkoxysilane and oxygen in a low-pressure vapor-phase deposition method is also known. In this case it is possible to form thin films even at low temperature and form thin films even on a glass substrate and on a polymeric film having poor heat resistance, being advantageous, however, the deposition temperature supposed to be suitable in this method is about 350° C. to 400° C. at the lowest, and the formed silicon oxide film is not necessarily satisfactory enough in planarity and film quality.
As a technique for improving film quality and embedding of an insulating film, a method for forming a silicon oxide film on a semiconductor substrate by CVD method where an organic alkoxysilane comprising one or more of straight-chain siloxane bond and ozone are reacted, is known. (For example, Patent document 1)
[Patent Document 1] JP-A H7-142578